[ 18/52] TTY: ttyprintk, dont touch behind tty->write_buf

[Greg Kroah-Hartman]

3.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jiri Slaby <jslaby@xxxxxxx>

commit ee8b593affdf893012e57f4c54a21984d1b0d92e upstream.

If a user provides a buffer larger than a tty->write_buf chunk and
passes '\r' at the end of the buffer, we touch an out-of-bound memory.

Add a check there to prevent this.

Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
Cc: Samo Pogacnik <samo_pogacnik@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/char/ttyprintk.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/char/ttyprintk.c
+++ b/drivers/char/ttyprintk.c
@@ -67,7 +67,7 @@ static int tpk_printk(const unsigned cha
 				tmp[tpk_curr + 1] = '\0';
 				printk(KERN_INFO "%s%s", tpk_tag, tmp);
 				tpk_curr = 0;
-				if (buf[i + 1] == '\n')
+				if ((i + 1) < count && buf[i + 1] == '\n')
 					i++;
 				break;
 			case '\n':


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